Solar systems which track apparent movement of the sun across the sky during the day typically use sensors to determine the position of the sun and adjust the solar system accordingly. A variety of techniques are currently used to operate solar systems. For example, sun position tables generated from known longitude and latitude can be used to predict the location of the sun during the course of the day. The deviation between predicted and actual position can be significant. Some sources of alignment error can be caused, for example, by inaccurate site location, contributions from an inclinometer, motor encoder, or other positioning equipment error. Although seemingly small, a single degree of alignment error can translate into an efficiency decrease of over 10%, particularly when aligning a solar concentrating system. Moreover, for solar concentrating systems, reduced alignment error permits accurate placement of concentrated sunlight. When concentrated sunlight can be directed more accurately, the associated solar cell and receiver can be of a smaller size than one which needs to be larger to allow for misaligned concentrated sunlight. The reduced size of the solar cell and receiver allows for cost savings in material and fabrication.
As an alternative to such dead reckoning techniques, feedback-based tracking systems are sometimes used. Such feedback systems can include cameras, which interpret visual imagery to locate the sun's position and align the solar system accordingly. Cameras are, however, typically expensive, and can require extensive and sophisticated signal processing to determine a precise solar position. Additionally, the camera element will encounter environmental effects which can decrease its efficacy as a sensor. Moreover, imprecision in mounting the camera also can result in alignment error.
Another feedback-based approach operates by inspecting the power generated by the system to determine the optimal alignment. Such power feedback systems typically intentionally introduce a small deviation to the system for the purpose of determining the peak power output based on alignment of the solar system. High speed electronics, which can be expensive, are required to perform the rapid inspection needed to determine the optimum alignment profile. Additionally, small changes in irradiance due to clouds or air masses can produce a condition similar to a misalignment condition, thereby confusing the tracker. Consequently, the tracker can introduce erroneous misalignment, thereby reducing efficiency.
Current tracking systems, therefore, can be expensive, introduce misalignment error even under optimal conditions, and can have sensitive components exposed to detrimental environmental conditions. Notwithstanding the difficulties in cheaply and accurately positioning a solar system, it is desirable to perform such tracking to increase the efficiency of the system.